In the formation of electronic circuits, integrated circuits or micro-circuits may be fabricated from thin semiconductor slices having a multiplicity of individual matrices or micro-circuits thereon. In usual practice, the slices contain multiple identical repeating matrices of the same type of micro-circuit or integrated circuit unit. The individual unit is sometimes referred to as an integrated circuit chip.
The present practice is to test each of the circuits of each integrated circuit chip formed on the semiconductor wafer prior to separating the wafer into the desired individual integrated circuit components. In some instances, an individual integrated circuit unit may contain multiple circuits, and it is therefore desirable to test each of the circuits of the integrated circuit unit before the wafer is cut into the individual integrated circuit units.
Since each micro-circuit of each wafer is normally positioned in a predetermined precise relation with respect to adjacent circuit units, it is possible to test the circuitry if a probe can be accurately located on each preselected point that corresponds to the circuit to be tested. It is possible, for example, to test several different circuits at the same time, or the same circuit of several different integrated circuit units. Thus, it is possible that adjacent probe arms may be positioned relatively closely to each other, in which event any capacitive coupling between adjacent probes should be avoided to obtain reliable test data.
The positioning of the probes must be quite accurate and also adjustable such that different integrated circuit units may be tested. Once the probes have been properly oriented, the wafer may then be stepped or moved from position to position so that each micro-circuit is properly located relative to the cooperative probe units for appropriate testing.
One of the difficulties experienced in the use of testing probes is that the point of the probe tip may form a scratch on the surface of the semiconductor wafer as it is contacted by the point. The semiconductor wafer is generally mounted on a platform that may be positioned precisely by an X-Y positioner relative to test probes which are fixedly mounted above the plane of the platform. When the platform has been moved to a desired position, the platform is then raised to bring specific locations on the surface of the semiconductor wafer into contact with the probe tips positioned above the platform. The probe tips are generally supported on the testing probes by an arm or arms such that a probe tip may move upwardly during contact of its point with the surface of the semiconductor wafer.
During upward movement of a probe tip with its point in contact with a semiconductor wafer, the point of the tip may undergo arcuate movement due to bending of the arm or arms that support the probe tip. As the point of the probe tip is moved arcuately, the point has both horizontal and vertical components of movement. The horizontal component of movement of the point is undesirable since this causes the point to move transversely relative to the surface of the semiconductor wafer to form a scratch on the surface. Such scratches are referred to as arcing of the semiconductor surface.
To prevent the problem of arcing during testing of integrated circuit components, it would be desirable if the probe or probe tip could be constructed such that the point of the probe tip would have essentially no horizontal movement during upward movement of the probe tip when in contact with the surface of a semiconductor wafer. This would maintain the point of the probe tip at the desired contact location on the surface of the semiconductor wafer without producing scratches or arcing of the surface.
A further problem which has been experienced in testing integrated circuit units has involved wearing of the point of a probe tip during repeated contacts of the point with surfaces of semiconductor wafers being tested. In probing a precisely positioned location on the surface of the semiconductor wafer, it is, of course, necessary that the point of the probe tip provide a small area which remains relatively constant in size during repeated probings. As the point of the probe tip begins to wear, the area on the integrated circuit that is contacted by the point may increase in size which is undesirable since this destroys the accuracy of the probing operation in which only a specific location on the surface of the semiconductor wafer is to be contacted. For this reason, it may be necessary to periodically replace probe tips when they become worn.
As stated, the test probes are generally mounted in a fixed position above the plane of a platform which supports a semiconductor wafer. In replacing a probe tip, it may be necessary to replace an entire test probe since the probe and probe tip may form an integral structure. When a test probe is replaced, it is necessary to reposition the probing apparatus accurately before its further use. During repositioning, it must be determined that the replacement probe is accurately positioned in the same location as the previous probe so that the replacement probe will contact the same desired location on the semiconductor wafer. The replacement of a test probe having a dulled tip is, thus, a time consuming operation.
In view of the time which is lost in repositioning a replacement test probe, it would be desirable if a test probe could be devised in which replacement of the probe would not be required merely because the point of the probe tip had become dulled. In accomplishing this result, it would be desirable if the element forming the point of the probe tip could be replaced without removing or replacing the test probe itself. If the element could simply be replaced by a sharp element positioned in the same precise location as the dulled element, this would result in a great savings in time by eliminating the time required to reposition a replacement test probe.
When the probe tip forms a point, such as a conical point, the area presented by the probe tip will vary in size depending upon the degree of wear or dullness of the point. This, then, makes it necessary to replace the element forming the point of the probe tip at regular intervals so that the area presented by the point remains relatively constant.
To alleviate the need for periodically changing the element that forms the point of a probe tip or of changing the test probe itself, it would be desirable if the element forming the point would present an area that remained relatively constant and did not change with wear of the tip. The element forming the point or the test probe itself would then not have to be replaced as frequently and the probing apparatus could be used more efficiently.